1. Field of the Invention
This invention relates to a vehicle lamp suitably used as a head lamp, and more particularly to a vehicle lamp using a discharge bulb as a light source in which the influence of electromagnetic waves is prevented.
2. Description of the Related Art
Recently, a study has been made to apply a discharge bulb, which is good in light-emitting efficiency, color rendering properties, and a long lifetime, as a head lamp for an automobile. However, in a lamp of this type, a high voltage is required for producing a discharge in a discharge bulb, and a lighting circuit need to be associated with the lamp in order to increase a voltage of a car-mount-type battery to a appropriate high voltage. In this lighting circuit, a high voltage is produced at its secondary side, and electromagnetic waves due to this high voltage are radiated to the exterior. The electromagnetic waves provide noises to affect various electronic equipment in an automobile, thus preventing the proper operation of these electronic equipment. For example, there is produced a so-called EMI trouble in which noises are produced in the radio or noises are included in a signal system in a microcomputer mounted on the automobile. Such electromagnetic waves are also produced in the discharge bulb supplied with the above high voltage, and the above-mentioned EMI trouble is caused by electromagnetic waves from the discharge bulb. Therefore, there has been proposed a construction in which a shield member is provided over an inner surface of a lamp body to cover the discharge bulb, or to cover the discharge bulb and a high-voltage connector connected thereto, or to cover the whole of the surrounding of a reflector with the discharge bulb, and the high-voltage connector. In this technique, the shield member suppresses the radiation of electromagnetic waves from the discharge bulb to its surroundings, so that the above EMI trouble can be dealt with.
In this conventional technique, in addition to the essential component parts of the lamp including the discharge bulb and high-voltage connector electrically connected thereto, the separate shield member for preventing the radiation of electromagnetic waves need to be prepared, and must be incorporated in the lamp, and this invites problems that the number of the component parts increases and that the time and labor required for the assembling operation increase. Moreover, the discharge bulb needs to be covered with the shield member and the reflector supporting the discharge bulb in an air-tight manner, and therefore there is required a connection structure for electronically connecting the shield member to the reflector. As a result, there are encountered problems that the construction of the lamp becomes complicated because of the provision of this connection structure and that the assembling operation is cumbersome. Since the position where the shield member and the reflector are electronically connected together is fixed, it is quite difficult to effect the electrical connection in a small space within the lamp body.